1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly to a method of fabricating a dielectric layer having a high dielectric property.
2. Description of the Prior Art
As generally known in the art, a dielectric layer is realized mainly by a SiO2 oxide film formed by oxidizing a silicon substrate, but such a SiO2 oxide film has a limitation in securing capacitance of a gate electrode.
Therefore, in order to solve this problem, techniques for using a nitride film or a Ta2O5 film, which has a high dielectric property, as a dielectric layer have been developed. However, when a single nitride film structure (an NO structure or an ONO structure) is employed as a dielectric layer, leakage current is caused because of pin holes, micro clacks, and so forth, which the nitride film itself has. Also, when the Ta2O5 film is employed as a dielectric layer, since the stoichiometric ratio of the Ta2O5 film itself is unstable, a breakdown strength characteristic is bad. Therefore, in this case, in order to secure a sufficiently high breakdown strength, low-temperature heat treatment at the temperature of 400° C. must be performed several times with high-temperature heat treatment at the temperature of 700˜900° C., so that the number of processes and an investment amount for equipment increase.